Objectives of this project are to identify populations with altered immunologic states who have excessive rates of malignancy and to identify the characteristics and possible determinants of any excess risk. We conducted a cohort study of 9,785 renal transplant recipients who were reported to a renal transplant registry over the past 20 years. The risk of reticulum cell sarcoma in this group of patients was 350 times greater than that expected based on the rates in the general population. This excessive lymphoma risk appeared within a year of transplant and remained at the same high level for the 5 or more years of follow-up. Other cancers were twice as common, due largely to soft- tissue sarcomas, hepatobiliary carcinomas, lower urinary tract carcinomas and adenocarcinomas of the lung. A study of patients with immune-deficiency syndromes has revealed a high risk of lymphoma, Hodgkin's disease, lymphatic leukemia (children), and stomach cancer (adults). Within the next year we will be utilizing the same resources to re- evaluate the cancer experience in the same manner and to identify characteristics of those patients who developed a malignancy vs. those who did not via analyses of case-control studies of these groups. Using another resource we will evaluate the cancer experiences of a hyperimmunized population.